I was thinking of assignin my groups acolytes to a PDF army, or an Imperial Guard regiment. I like the Vitrian Draggons (Gaunt's Ghosts - First and Only) anyideas on how 2 make them, and a quick way of designin NPCs for them?

I'd say 2 options: a rank 0 alternate rank, or a background package. Aren't the Vitrian Dragoons the ones from the Sabbat Worlds crusade with the cool glass armour? If so, you might also have to write up some quick rules for that armour and swap it for the normal Guarsman's armour. Other than that, the standard guardsman's basic career should work. As for a basic Guardsman profile, there's one in Deathwatch, and there are profiles for the Maccabean Jannisaries in the most recent DH adventure book...mind you the latter might be a bit better than normal guardsmen, I get the impression they're a bit of an elite unit.

I would agree with the Background Package idea. To make the kind of package you want, just look at some of the other background packages (in Inquisitor's handbook and Radical's handbook) and then follow that template.

If memory serves, the Vitrian Dragoons are a semi-elite heavy assault IG unit with fancy "glass-steel" armour that vaguely resembled stained glass cathedral windows.

If everyone in the game is going to share this origin then I would avoid the "background package" route, instead just making it a "template" that is layered over the base character. The key points:

Drive (Ground), Basic (Las), Melee (Primitive), CLore (Imperial Guard) They all start with this for free.

Replace starting armour with: Vitrian Carapace (AP 5 all)

Choice of: Mark III Lasgun OR Laspistol and Sword PLUS Knife

Add Imperial Infantryman's Uplifting Primmer (Sabbat Worlds Crusade edition) to starting gear.

If only some of the characters are going to be Dragoons then perhaps charge 100xp for this as a background package? It should be fairly cheap as one of the skills and two of the talents are already included in the stock Guardsman beginning package.

I seem to remember the battledress worn under their distinctive armour as well as their dress uniforms being red... Stylish AND practical when you bleed on them.